Methanol synthesis

ABSTRACT

A process for the synthesis of methanol in which water in liquid is reacted with gaseous carbon monoxide in the presence of a select carbon monoxide shift catalyst at temperatures of 180*380* C. and pressures above about 250 atmospheres.

United States Patent Tarhan Sept. 5, 1972 [54] METHANOL SYNTHESIS [72] Inventor: Mehmet Orhan Tarhan, Bethlehem,

[73] Assignee: Bethlehem Steel Corporation [22] Filed: Dec. 11, 1970 [21] Appl. No.: 97,367

[52] US. Cl ..260/632 R, 23/213, 252/373, 260/449.5

[51] Int. Cl. ..'....C07c 31/04, C07c 31/06 [58] Field of Search ..260/632 R, 449.5; 23/213 [56] I References Cited UNITED STATES PATENTS 1,797,426 3/1931 Larson ..23/213 11/1970 Fenton .....23/213 10/1971 Skinner ..260/449.5

FOREIGN PATENTS OR APPLICATIONS 738,023 10/1955 Great Britain ..260/449.5 739,487 7/1966 Canada ..260/449.5

Primary Examiner-Leon Zitver Assistant Examiner-Joseph E. Evans Attorney-Joseph J. OKeeffe [57] ABSTRACT 3 Claims, No Drawings METI-IANOL SYNTHESIS BACKGROUND OF THE INVENTION This invention relates to methanol synthesis.

Methanol synthesis is well known in the art. However, prior art methanol synthesis has been directed to processes in which the reactants are gases. It has been customary, in prior art methanol synthesis, to have, as a first step, the production of synthesis gas. Synthesis gas, a mixture of hydrogen and carbon oxides, is obtained from such sources as the catalytic reaction of steam and natural gas, or the catalytic reaction of steam and carbon monoxide. When using carbon monoxide and steam as the raw materials for synthesis gas, carbon monoxide is reacted with steam in a gas phase reaction at pressures of 10-35 atmospheres and temperature from 180-400 C. to produce hydrogen and carbon dioxide, according to the equation:

H O(steam) +CO H +CO 1 The carbon dioxide of equation 1 is at least partially removed and the hydrogen produced by equation 1 reaction is then mixed with carbon monoxide to form methanol synthesis gas. The reaction of equation 1 is commonly called the carbon monoxide shift reaction. Reaction 1 is reversible and takes place in the gas phase in the presence of a catalyst such as chrome oxide promoted iron oxide or the binary and ternary combinations of the prereduced oxides of copper, zinc and chrome.

In the course of synthesizing methanol from synthesis gas, the synthesis gas is compressed, and then reacted over a catalyst to form methanol according to the equations:

C 2 H CH OH (2) and CO2 3 H2 H20 (3) These prior art methods of methanol synthesis have many disadvantages.

The major disadvantage derives from the fact that a two-step synthesis (manufacture of synthesis gas followed by conversion of synthesis gas to methanol) is inherently complicated and costly.

A further disadvantage results from both steps of the prior art methanol synthesis being carried out in gas phase. Such a process requires the expense of handling and compressing large volumes of gaseous materials, including large amounts of steam.

Still another disadvantage of prior art methanol synthesis is that both synthesis steps provide exothermic reactions which must therefore be carefully controlled to prevent runaway reactions.

SUMMARY OF THE INVENTION 1 have discovered that the aforementioned disadvantages of the prior art can be overcome by the onestep method of this invention in which carbon monoxide and liquid water are combined and catalytically reacted at pressures of about 250 to 700 atmospheres and temperatures from about 180 to about 380 C. Catalysts suitable for my method are binary combinations of oxides of copper and zinc, and copper and chrome, in their respective prereduced forms, and ternary combinations. The overall reaction equation is:

3 C0 2 H O (liquid) 2 C0,+Cl-I,OH 4 In the practice of my method, I use catalysts which,

heretofore, have been used exclusively for gas phase catalysts, designed exclusively for gas phase reactions,

upon introduction into liquid water, tend to lose their solid structure and eventually acquire a powdery nature. I have discovered that, contrary to prior art teaching, they do not lose their activity.

My invention has the following advantages over the prior art synthetic processes:

First, it achieves the synthesis of methanol in one step, directly from carbon monoxide and liquid water, thus considerably simplifying the synthesis and drastically reducing its costs;

Second, the introduction of raw material water in liquid form eliminates the need for steam generation facilities and improves the thermal efficiency of the process;

Third, the lower exothermic heat of reaction simplifies the problem of heat removal. In addition, liquidphase reactors lend themselves to efiicient heat removal; these two factors lead to an overall reaction that is more readily controllable.

In the following examples, pressure refers to gauge unless otherwise noted.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the following specific example by which my method may be practiced, 25 grams of a catalyst consisting of the oxides of copper and zinc in prereduced form (Chemetrons G-66-RS) was mixed with grams distilled water. Twenty-two and seven-tenths grams (22.7) ofcarbon monoxide (99.5 percent purity) was introduced into the water and catalyst mixture.

same batch reactor and in the same manner as example 1. Twenty-five grams of a catalyst consisting of the prereduced oxides of copper and chrome (Chemetrons GT-531 cu-chromite) were used and a temperature of 295 C. and a pressure of 420 atmosphere, gauge, was maintained for 30 minutes. Two and one-half (2.5) percent of the carbon monoxide was converted to methanol.

It is contemplated that the method of my invention could be practiced in a continuous manner by feeding liquid water through a preheating zone to a reaction zone of a pressure vessel. The pressure vessel would contain a stirred or slurried bed of prereduced copper oxide-zinc oxide or similar catalyst. Similarly, purified carbon monoxide would be fed continuously through a preheating zone to the reaction zone in a molar ratio of 3 carbon monoxide to 2 water. Reaction zone temperatures and pressure would be maintained at about 300 C. and 400 atmospheres, gauge, respectively. Means, such as turbine-type gas dispersers, would be provided to .bring about intensive contact between the gas and the liquid phases in the reaction zone. Reaction products would be withdrawn from the reaction zone, and would be processed by means well known in the art to remove the carbon dioxide, to purify the product methanol, and to recycle unreacted water to the reaction zone.

The stoichiometry of reaction 4 requires that 2 moles of carbon dioxide be removed from the reaction zone for 3 moles of carbon monoxide reacted. If, however, the feed gas contains some hydrogen, in addition to carbon monoxide, there is no need to remove all the carbon dioxide formed, since the hydrogen in the feed could react with it, and produce additional methanol.

I claim:

1. A process for synthesizing methanol comprising:

a. reacting carbon monoxide with liquid water in the presence of a catalyst selected from the group consisting of prereduced mixed oxides of copper and zinc, copper and chromium, and copper, zinc and chromium at a temperature of about to 380 C. and a pressure of about 250 atmospheres to about 700 atmospheres.

2. A process for synthesizing methanol comprising:

a. forming a mixture of liquid water and a catalyst selected from the group consisting of the prereduced mixed oxides of copper and zinc, copper and chromium, and copper, zinc and chromium,

b. introducing carbon monoxide into the mixture;

0. reacting the carbon monoxide with the mixture at a temperature of about 180 to a bout 380 C. and a pressure of about 250 atmospheres to about 700 atmospheres to form methanol.

3. A process for synthesizing methanol comprising reacting liquid water with carbon monoxide in the presence of a catalyst consisting of the prereduced mixed oxides of copper and zinc at-a temperature of about 300 C. and a pressure of about 420 atmospheres. 

2. A process for synthesizing methanol comprising: a. forming a mixture of liquid water and a catalyst selected from the group consisting of the prereduced mixed oxides of copper and zinc, copper and chromium, and copper, zinc and chromium, b. introducing carbon monoxide into the mixture; c. reacting the carbon monoxide with the mixture at a temperature of about 180* to a bout 380* C. and a pressure of about 250 atmospheres to about 700 atmospheres to form methanol.
 3. A process for synthesizing methanol comprising reacting liquid water with carbon monoxide in the presence of a catalyst consisting of the prereduced mixed oxides of copper and zinc at a temperature of about 300* C. and a pressure of about 420 atmospheres. 